The invention relates to sheet metal can bodies such as are used to contain processed foods or beverages.
GB 2 237 550 describes a can body in which the side wall includes a plurality of adjacent panels in the form of single concave flutes. Each flute is defined laterally on each side by a convex rib lying on the cylindrical envelope of the side wall. The panels tend to flex in groups when the can body is subject to an internal pressure reduction and return to their relaxed position when the pressure reduction is relieved.
The present invention relates to a modification of the can body of GB 2 237 550 which has particular application where an internal pressure reduction is maintained in a can body after processing of the food or beverage therein is complete and the can has returned to ambient temperature. This occurs for example in the case of hot filling of eg fruit juices. Pressure reduction after processing may also be obtained as a result of the can volume increasing during processing due to a high internal pressure causing expansion of the can ends and side wall.
A prior solution to the problem of residual internal pressure reduction in can bodies is described in U.S. Pat. No. 4,836,398. In this solution the bottom wall of the can body is reformed after filling and sealing to increase the internal pressure. This requires the provision of a specially formed bottom wall and adds an additional step to the process of filling cans.